PopulationPopulation andand ClimateClimate Change:Change: CouplingCoupling PopulationPopulation ModelsModels withwith EarthEarth SystemSystem ModelsModels

Safa Motesharrei, Jorge Rivas, Fang Zhao, Eugenia Kalnay, Victor Yakovenko, Matthias Ruth Ning Zeng, Fernando Miralles-Wilhelm, Cortney Gustafson, Bob Cahalan

WCRP 28 October 2011 Without fully coupling we could not predict ENSO!

We are still missing the most important component of the Earth System: the Human System growth

1AD 0.3b 1650 0.5b 1800 1.0b 1927 2.0b 1960 3.0b 1975 4.0b 1987 5.0b 1998 6.0b 2011 7.0b Population and climate: a study at the London School of Economics Per dollar spent, reduces four times as much carbon over the next 40 years as adopting low-carbon technologies 2010 UN medium projection Concluded: Family planning is cost effective and should be a primary method to reduce 2006 UN medium projection emissions Copenhagen: no discussion on population or family planning: it is a taboo subject New UN projection is higher Why was the population able to grow so fast since the 1950’s? Two reasons: 1) Sanitation and antibiotics (living longer) 2) Use of fossil fuels in agriculture starting in the 1950’s: - fertilizers, pesticides, irrigation, mechanization (). 1950 to 1984: production of grains increased by 250% and the population doubled Without fossil fuels population would be much smaller! • Growth in grain production is now flattening out • Industrial farming is destroying forests, soil • Urban and suburban sprawl is overrunning best farmland This is not sustainable: “We are drawing down the stock of natural capital as if it was infinite” (Herman Daly) Example: North Korea, got cheap oil from the former Soviet Union until early 1990s

Source: FAO, www.wolfatthedoor.org.uk

Production of grain in North Korea, updated to 2008

The famines in North Korea are the result of the sudden loss of access to abundant fossil fuel 1972: Club of Rome “Limits to Growth”

The Club of Rome commissioned a group at the MIT Sloan School of Management to study: “Are current policies leading to a sustainable future or to collapse?”

When the results appeared in 1972, the conclusion that with finite natural resources growth would and collapse was dismissed as absurd by many economists. (“discredited”)

35 years later the “standard run” model compares well with reality for all variables. (Graham Turner, G.E.C., 2008) The model could have four possible types of outcomes

Infinite World Ideal (no overshoot)

You are here… Or here…

Hopefully… Disaster The results are sobering: most scenarios collapse Even if resources are doubled, collapse is only postponed ~20 years

In order to avoid collapse, government policies are needed to: • Stabilize population and • Stabilize industrial production per person • Adopt technologies to – abate – conserve resources – increase land yield – protect agricultural land Standard Neoclassical As Herman Daly, Robert Costanza, and other scholars in the field of describe,

Goods and Services

Firms: Households:

Labor and Capital

The standard Neoclassical Economic Model does not account for: • Inputs (resources) • Outputs (pollution) • Stocks of Natural Capital • Dissipation of Energy (i.e., a Perpetual Motion Machine) • Depletion, Destruction or Transformation of Matter Therefore, no effects on the Earth System, and No Limits to Growth. Realistic Ecological Economic Model (Herman Daly) • Incorporates INPUTS, including DEPLETION of SOURCES • Incorporates OUTPUTS, including POLLUTION of SINKS

Sources: Stock of Natural Capital Flows of Energy

Inputs: Outputs: 1. Energy 1. Emissions Oil, Coal, Gas, Population óTechnology CO2, Methane, etc Nuclear, , rate Renewables, etc 2. Waste Products Energy Use / Capita Garbage, Toxics, etc Resource Use / Capita 3. Surface Changes 2. Matter Emissions produced / Capita Soil, Minerals, , Waste produced / Capita , Lumber, and Economic expansion / Capita Other Materials , etc Resources

Sinks: Oceans, Atmosphere Land Feedbacks in an Ecological Economic Model Of course, the OUTPUTS and the filling up of SINKS, have feedbacks on the Human Economy, the Quantity and Quality of the INPUTS, and the depletion of SOURCES :

Sources: Stock of Natural Capital Flows of Energy

Inputs: Outputs: 1. Energy 1. Emissions Oil, Coal, Gas, Population óTechnology CO2, Methane, etc Nuclear, Biomass, Population growth rate Renewables, etc 2. Waste Products Energy Use / Capita Garbage, Toxics, etc Resource Use / Capita 3. Surface Changes 2. Matter Emissions / Capita Soil, Minerals, Urbanization, Waste / Capita Deforestation, Lumber, and Economic expansion / Capita Other Material Desertification, etc Resources

Sinks: Oceans, Atmosphere Land “Empty World” Model • Throughout most of human history, the Human Economy was so small relative to the Earth System, that it had little impact on the Sources and Sinks. • In this scenario, the standard isolated economic model might have made sense.

Sources:

Inputs: Outputs:

Sinks: But Population and Economic Output per Capita have grown, and the net impact is their product!

Technology allows more efficient production, but also much faster consumption! “Full World” Ecological Economic Model • Today, the Human Economy has grown so large, it has very large Effects on the Earth System, Depleting the Sources and Filling the Sinks. It is clear that growth cannot continue forever.

Sources:

Outputs: Inputs:

Sinks: Regional Population Models with two-way coupling is needed!

Global Global Sinks: Sources: Oceans, Atmosphere Land

Inputs ó Outputs: Pop Techn Inputs Pop óTechn Outputs: REGION 1 … REGION N

Local Local Sinks: Local Local Sinks: Oceans, Sources: Oceans, Atmosphere Sources: Atmosphere Land Land Some of the Essential Feedbacks needed

• Vegetation <=> albedo (climate change) • CO2 emissions <=> climate change <=> vegetation • Vegetation <=> water use, fossil fuel use <=> crops • Population <=> crops, food/capita <=> mortality • Population <=> food/capita <=> fisheries • Population <=> CO2 emission, pollution <=> atmosphere, land • Population <=> <=> loss of cultivated land • Technology <=> non-renewable resources <=> alternative resources • Policies <=> education, birth rate <=> pollution, emissions • Resource depletion <=> trade, resource conflicts • Population <=> CO2 emissions <=> climate change <=> vulnerability

We proposed to experiment first using an intermediate Earth System model (Speedy-VEGAS) and a prototype Human-Economy-Population model.

Government policies are important!

The red (highest NDVI vegetation index) is in the province of Misiones, Argentina, that protects the forest. Compare Misiones with Brazil, Paraguay and the rest of Argentina! Coupled Simple Water Submodel (SIWA) Earth System Human System UMD/ICTP Population

Demographics

Net Water Atmosphere Demand Water/capita

Techn Freshwater Efficiency Collection Treatment

Evaporation Distribut Fresh Pipeline Avail. Consumed Precipitation Water Water Enough? Supply Water Water If not, Increase use/ Sources Increase technology River inflow Waste Water Leaks River outflow Treatment

Waste Water Recycling Waste Land Model Water

Runoff

Oceans Human and Nature Dynamical model (HANDY) with Rich and Poor: for thought experiments

Just 4 equations! Total population: Rich +Poor x = xR + xP Nature equation: (only the poor produce!) y Regeneration y(1 y) Production x y ! = ! " " # P The Wealth belongs to the Rich: Inequality factor ! ~ 100 W! = Production - Poor consumption - Rich consumption =!x y " sx "# sx p p R Population equations: death rate depends on whether there is enough food:

x!P = !" P xP + #P xP x x x !R = !" R R + #R R

The rich elite accumulates wealth from the work of everyone else (here referred to as the poor). When there is a crisis (e.g., famine) the elite can spend the accumulated wealth to buy food. Human and Nature Dynamical model (HANDY) with Rich and Poor: a thought experiment

Rich Poor Poor Population Nature Wealth Nature Wealth

Rich Population Human and Nature Dynamical model (HANDY) with Rich and Poor: a thought experiment

• Nature declines with population growth Poor Nature • Using their wealth, the Rich can shield themselves from environmental Wealth Rich degradation, which first affects the poor • Eventually it reaches the upper classes as well, when it is too late to take preventive measures

By the end of the 20th century, having surpassed the sustainable of the planet, the population is drawing down the accumulated capital to survive Human and Nature Dynamical model (HANDY) with Rich and Poor: a thought experiment

• Nature declines with population growth Poor Nature • Using their wealth, the Rich can shield themselves from environmental Wealth Rich degradation, which first affects the poor • Eventually it reaches the upper classes as well, when it is too late to take preventive measures

This thought experiment shows how a crisis can happen rapidly, even though it appears that population is rising steadily without any problems, and that the wealthy would not feel the effects of the collapse until it is too late for the poor (and then it is too late for the rich as well!). AnalogyAnalogy betweenbetween atomicatomic distributiondistribution ofof energyenergy andand thethe distributiondistribution ofof incomeincome ((YakovenkoYakovenko etet al.,al., 2000,2000, ……))

• Atoms in a gas are identical, but the probability distribution P(E) of their energies E is highly unequal, with few atoms having high energies and many atoms having low energies. • In statistical physics, P(E) is given by the exponential Boltzmann-Gibbs distribution following from maximization of entropy in the ensemble of interacting atoms. • Yakovenko applied a similar probabilistic approach to ensembles of interacting economic agents (i.e., people), with remarkable agreement with IRS data Yakovenko (2000) applied a similar probabilistic approach to ensembles of interacting economic agents and obtained probability distributions that are in remarkable agreement with the empirical data

“the bottom 97%”

“the top 3%”

An analysis between 1983 and 2003 of IRS data shows that the inequality increased and all the growth went to the top 3%

Gini coefficient of inequality (increases)

Exponent of the Pareto distribution

Percentage of total income in the “rich tail”

OurOur plansplans • Continue developing the submodels of the Prototype Human system and fully coupling with the Earth System. • Post the codes… • Couple the Yakovenko statistical model with the HANDY model first, replacing the Rich/Poor classes with realistic continuum wealth distributions. • Apply the same statistical analysis to the full prototype coupled system. • We welcome multidisciplinary collaborations!